---
header: Special Service Guide Update for December 5, 2016
lang: en
last_updated: null
url: https://docs.fastly.com/changes/significant/2016/12/05/changes
---

We recently updated our guide describing [how we calculate your bill](https://docs.fastly.com/products/how-we-calculate-your-delivery-bill).

Beginning on and continuing after February 1, 2017, Fastly will use [The International System of Units](https://www.bipm.org/en/measurement-units) (SI Units) to measure bandwidth. In our calculations, 1 gigabyte (GB) = 10<sup>9</sup> (1,000,000,000) bytes, 1 terabyte (TB) = 10<sup>12</sup> bytes (or 1,000 GB), and 1 petabyte (PB) = 10<sup>15</sup> bytes (or 1,000 TB). This change will align our customers' invoice usage with the usage shown on the Stats page. At this point, Fastly will begin measuring and charging for bandwidth related to HTTP requests to our customers' origins from the CDN.

Through January 31, 2017, Fastly will continue to use the [IEC prefixes](https://www.nist.gov/pml/owm/metric-si-prefixes) for binary powers, starting with 1 gibibyte (GiB) = 2<sup>30</sup> (1,073,741,824) bytes and will not charge for bandwidth related to HTTP requests to our customers' origins from the CDN.